Browse

121 - 130 of 80,778 items

Acquisition and Tracking Performance of Satellite Navigation System Signal using Tiered Differential Polyphase Code

Abstract

In this paper, we analyze the acquisition and tracking performance of signal using a tiered differential polyphase code as the secondary code. The Zadoff-Chu sequence is known to have a CAZAC (Constant Amplitude Zero Auto-Correlation) characteristics. The secondary code generated by differential encoding of the Zadoff-Chu sequence also has the same characteristics as the Zadoff-Chu sequence. Therefore, long integration will give better correlation results. We compare signal acquisition and tracking performance when using the NH sequence and Zadoff-Chu sequence as the secondary code. Monte-carlo simulation is performed using MATLAB. We use the probability of detection and the mean acquisition time for signal acquisition performance and tracking jitter for signal tracking performance.

Open access
Acrylic sculpting nails, an occupational hazard for contact dermatitis. Case reports and review of the literature

Abstract

Acrylates are plastic materials formed by the polymerization of monomers, which are recognized as powerful sensitizers that may cause allergic contact dermatitis both in occupational and non-occupational environment. In the occupational setting, the most exposed workers are the dentists, dental technicians, prosthesis technicians, printers, painters, fiberglass workers and nail technicians. We describe four cases of occupational allergic contact dermatitis in nail technicians caused by acrylic compounds that illustrate numerous clinical manifestations. Clinical manifestations ranged from edema, erythema, scaling and fissuring fingertips to erythematous patches around the chin, mandible and abdomen. Patch testing results revealed positive reaction to 2-hydroxyethyl methacrylate in all patients. Of the four patients, two changed jobs, one stopped exposure because of pregnancy and one patient continued working, showing no improvement, despite undergoing treatment. These cases underline the importance of improvement of preventive measures in the workplace.

Open access
Advanced Multi-Engine Platform (AMP™) – A Way to Robust RTK

Abstract

The paper describes the Advanced Multi-Engine Platform (AMP) – Topcon’s patent pending technique, which is capable to improve RTK performance, based on the idea of running several RTK engines in parallel. The performance of AMP is dependent on Topcon receiver board, where it has been implemented, and the best results are achieved with B210 board. The main specifics of B210 is that it has two RF front-ends and a single digital section. Such an architecture allows for calculating heading and tilt within a single receiver board, and providing better RTK performance due to synergy of attitude determination and RTK solutions from two antennas, calculated within a single digital section. The paper describes specifics of B210 board along with mathematical aspects of AMP and its logic. The test results demonstrate noticeable improvements in RTK performance for B210 receiver board with AMP, compared with the classical single-engine RTK approach.

Open access
AIOSAT - Autonomous Indoor & Outdoor Safety Tracking System

Abstract

Even though satellite-based positioning increases rescue workers’ safety and efficiency, signal availability, reliability, and accuracy are often poor during fire operations, due to terrain formation, natural and structural obstacles or even the conditions of the operation. In central Europe, the stakeholders report a strong necessity to complement the location for mixed indoor-outdoor and GNSS blocked scenarios. As such, location information often needs to be augmented. For that, European Global Navigation Satellite System Galileo could help by improving the availability of the satellites with different features. Moreover, a multi-sensored collaborative system could also take advantage of the rescue personnel who are already involved in firefighting and complement the input data for positioning.

The Autonomous Indoor & Outdoor Safety Tracking System (AIOSAT) is a multinational project founded through the Horizon 2020 program, with seven partners from Spain, Netherlands and Belgium. It is reaching the first year of progress (out of 3) and the overarching objective of AIOSAT system is to advance beyond the state of the art in tracking rescue workers by creating a high availability and high integrity team positioning and tracking system. On the system level approach, this goal is achieved by fusing the GNSS, EDAS/EGNOS, pedestrian dead reckoning and ultra-wide band ranging information, possibly augmented with map data. The system should be able to work both inside buildings and rural areas, which are the test cases defined by the final users involved in the consortium and the advisory board panel of the project

Open access
Amorphous silicon PEC-PV hybrid structure for photo-electrochemical water splitting

Abstract

The paper presents fabrication and characterization of amorphous silicon carbide (a-SiC:H) based structures for photo-electrochemical (PEC) water splitting. The increase of the photocurrent of PEC upon the decreased of CH4 flow during the deposition is associated with the decrease of the band gap and increased absorption of light in a-SiC:H. Photocurrent of 50 µA/cm2 is achieved for PEC structure prepared with the lowest CH4 flow during the deposition. An ITO/a-SiC:H/Si silicon heterojunction structure forming a simple photovoltaic cell (PV) with efficiency of 9.66% was prepared to support additional voltage hereby forming a hybrid PEC-PV system. ASA simulation revealed that a photocurrent of 0.62 mA/cm2 and solar to hydrogen efficiency of 0.76% can be achieved for hybrid a PEC-PV structure with 5 PVs connected in series behind the PEC cell. Further opportunities for increasing the performance are discussed and summarized.

Open access
Analytical - diffraction model of V-band propagation for the Radiocommunication Events Management System (REMS)

Abstract

The paper presents an analytical-diffraction propagation model for the needs of the Radiocommunication Events Management System, for coast and ship radio stations in sea area A1. The V-wave propagation in sea area 1 has been analyzed as part of an analysis of ranges of particular radio stations and their ability to establish radio contact. The theoretical basis and assumptions on which the model structure design process is based have been presented. Methods of modelling and presentation of dislocation of particular radio stations and their ranges have been discussed.

Open access
Approximate methods for the optical characterization of inhomogeneous thin films: Applications to silicon nitride films

Abstract

In this paper the overview of the most important approximate methods for the optical characterization of inhomogeneous thin films is presented. The following approximate methods are introduced: Wentzel–Kramers–Brillouin–Jeffreys approximation, method based on substituting inhomogeneous thin films by multilayer systems, method based on modifying recursive approach and method utilizing multiple-beam interference model. Principles and mathematical formulations of these methods are described. A comparison of these methods is carried out from the practical point of view, ie advantages and disadvantages of individual methods are discussed. Examples of the optical characterization of three inhomogeneous thin films consisting of non-stoichiometric silicon nitride are introduced in order to illustrate efficiency and practical meaning of the presented approximate methods.

Open access
Black silicon – correlation between microstructure and Raman scattering

Abstract

Black silicon layers were formed on silicon substrate by the surface structure chemical transfer method and by anodic etching method. Properties of microstructure of formed layers were experimentally studied by the electron microscopy methods (TEM) and characterized by statistical, Fourier and multifractal methods. Theoretical structures with defined fractal properties and surface roughness were generated and their microstructure properties were evaluated. Obtained results were used for the explanation of the real structure development during the forming procedure. By using of this approach, we study the correlation of roughness and fractality with optical properties. Black silicon layers were also investigated by using of Raman scattering method. Optimized theoretical model describing the 1st order of black Si Raman scattering profile was constructed and used for evaluation of the biaxial tensile stress introduced during etching procedure.

Open access
Characterization of nanoblisters on HOPG surface

Abstract

We report on influence of the surface functionalization on the properties of highly oriented pyrolytic graphite. The samples were processed in nitric acid and characterized by XPS, Raman and EDX spectroscopies, AFM, SEM and optical microscopy. It is shown that interaction of nitric acid with the surface of HOPG leads to two types of reactions: oxidation of the graphite and intercalation of the nitrate ions at the blistered areas.

Open access
Communication with superiors and colleagues and other occupational stressors. Correlations with work ability, self-efficacy and health in employees from primary and secondary education

Abstract

During periodic occupational medical checkup, in a sample including all employees from two high schools, a secondary school and a kindergarten, we administered through voluntary completion, questionnaires which assessed the employees’ occupational stress in terms of individual characteristics, anxiety, sense of self-efficacy, work ability, emotional exhaustion and health status (using ShortForm 36 questionnaire). A number of 233 questionnaires were returned. Only the occupational stressor represented by communication with superiors correlates significantly negatively with work ability in all four units. Work ability and communication with superiors also have average scores which differ significantly and are concordant in all four units. In the secondary school, work ability has the highest average value and the lowest average value of “communication with superiors” stressor. The same values are decreasing for WAI in order, from high school 2 to high school 1 and kindergarten while the stressor represented by communication with superiors has increasing values in order from high school no 2 to high school no. 1, and kindergarten. These results show that programmes to reduce occupational stress in school units should primarily address the school unit leadership in order to improve their communication with employees.

Open access